The present invention relates to pneumatic tires and, more particularly, to pneumatic tractor tires designed for use on the drive axles of farm tractors and similar vehicles.
To enable tractors to pull plows and other like farming implements through the ground, it is necessary to provide tires on the tractor drive axle which develop sufficient traction in the soil under the encountered load conditions. Typically, this property is sought to be satisfied by a tire tread design and construction providing on the tread generally transverse, discrete lugs which are capable of biting into the soil on which the tractor is operated for most farming uses. A variety of such lug tread designs have been utilized or proposed in the art for purpose of increasing traction through improved biting capability and effective expulsion of earth from the deep recesses between the lugs of the tread. Such designs also are required to take into account the wear characteristics of the tread lugs.
The utilization of lugs raised substantially above the base tread surface so as to improve the traction of tractor tires in generally encountered soil conditions is known to introduce tire and vehicle vibrations which affect ride comfort and stability of the tractor, and stress the drive axle. Vibration of this type is most noticeable when the tractor is driven on hard soil or paved surfaces as it occasionally must be, particularly at speeds above, say, ten miles per hour, but also can be encountered in normal operations in the generally soft soil for which the tires are designed. Often, designers and manufacturers of pneumatic tractor tires face a compromise situation between traction capability on the one hand and minimized vibration/maximized stability on the other. See, for example, U.S. Pat. Nos. 4,383,567 to Crum, et al.; 4,480,672 to Marshall, et al.; and 4,534,392 to Bonko, et al.